The invention is related to the field of analog-to-digital converters (ADCs), and in particular to ADCs supporting multi-input and multi-output systems.
Multi-input multi-output (MIMO) systems offer advantages to wireless receivers such as improved data rates or improved channel reliability. Such systems rely on the use of multiple antennae having special separation that effectively create multiple communication channels between the transmitters and receivers. These channels can be utilized to then achieve the advantage mentioned above.
The use of multiple antennae is generally implies the use of multiple receiver building blocks from the RF frontend all the way to the ADC. This results in an increase in area, cost, and power consumption of the receiver. A number of solutions have been proposed to mitigate the impact of these increases, which revolve around the idea of multiplexing. Multiplexing allows for a single receiver to be shared with multiple antennae. The idea's include time division, frequency division, and code division multiplexing. Although these techniques do reduce the area of the receiver, they degrade the signal-to-noise performance.
The present invention offers a solution where a reduction in MIMO ADC area and power is achieved while the signal-to-noise ratio remains unchanged. This solution is based on the use of noise coupled delta-sigma ADCs as will be explained next.